Half way through this season and I have picked up some audio noise in the in-boats speakers only. It's kind of a fuzzy, sometimes crackling noise. It doesn't change with volume, but does tend to be less audible with certain music. It's most noticeable when no music is playing. I can fade the in-boats out and the noise goes away. I've tried everything I know to test for bad parts, but can't seem to corner the problem. There is no noise when I plug an iPod directly to the amp. I tried swapping RCAs with another amp and the problem didn't flow the RCAs. All my stereo components are wired to a common power point (fixed that last season). I've read out the RCAs with a multi-meter and none are shorted to ground. I did have varying ohm valves between different sets of RCAs (from 22-35 ohms), but no short. My EQ is just an old Clarion unit a friend gave me years ago. Could that be causing some kind of interference with only the in-boat speakers? Nothing has changed about my system this season, no cabling or wires moved, just this noise. Once again, I hear noise in only the 6 in-boat speakers, not in the subs or tower.

Ipod direct to amp = noise gone would indicate the noise is upstream, but yet is did not move to another amp when you swapped RCA cables. Describe the noise. Is all the time, engine running, engine off, static, whine, etc?

Ipod direct to amp = noise gone would indicate the noise is upstream, but yet is did not move to another amp when you swapped RCA cables. Describe the noise. Is all the time, engine running, engine off, static, whine, etc?

The noise is present with or without the engine running. For the most part it sounds like radio static if you weren't tuned in to a station just right. It will change sound levels periodically without changing volume. Sometimes there is a whine, but not offen.When playing music it isn't noticable unless a quiet portion of the song is playing. It goes away when the RCAs are unplugged from the amp or I fade out the in-boat amp.

The EQ seems to be the only part I haven't taken out of the equation. I'm going to unplug the RCAs from the EQ and use an iPod there to make positive the RCAs aren't the problem and take the EQ out of it.

iPod straight to the amp = No noise
iPod straight to amp via RCAs from EQ = No noise
Unplug RCAs from amp = No noise (noise goes away when Left RCA is unplugged)
Unplug RCAs from EQ = Noise, but not as much
RCAs from EQ to amp = Noise
Spare RCAs from EQ to amp = Noise
Swap in-boat and tower RCAs at EQ = No change, noise still in in-boats only

At this point I'm scratching my head. One test will make you narrow it down to a certain component or part, only to have another test kill that theory. Any ideas?

Sounds like the eq is going bad on the cabin channels. Try bypassing the eq for the cabins and going straight to the headunit?

I thought so as well, until I swapped the in-boat and tower RCAs on the back of the EQ thinking if the EQ was the cause the noise should move to the tower. No such luck! The noise stayed in the in-boats. That made me believe the RCAs were the problem until I removed the RCAs from the back of the EQ and plugged an iPod directly into them. No noise!

One thing that has me scratching my head is when I remove the left RCA from either the amp or EQ for the in-boats the sound goes away.

Okay, with the in-boat amp connected directly to the HU I still get noise. There is not as much output (volume) from the speakers compared to going through the EQ but I guess that is because the line voltage is lower. I may try to borrow an EQ this weekend just to test if that is the culprit or not.

Yes, all stereo equipment is wired to the same power distributuion. I had that issue last season and fixed it, but then all the speakers had noise in them. Once I fixed that the system was noise free for a year. I have changed nothing in the system to cause this noise. I just noticed it one day earlier this season and it has been there ever since. I don't think this is a grounding issue.

The reason I don't use a charger is becasue the one time I did (charging while using 3.5mm jack) I did get noise, but that was long before this new stereo setup.

Ha, well I'm tapped then man. Honestly my personal wild guess is that it's something with your cabin amp, but that's just a guess (based on the fact you get the sound from both the HU and EQ). Would be interesting to see whether the sound went away with a different amp, but that is a more expensive experiment.

Jason,
I'm going to make a few assumptions here including:
When you say the boat is not running you also mean that the key was completely 'Off' yet there is still noise.
When you reversed the RCAs at the EQ end, you also reversed the in-boat and tower output sections of the EQ and tried it playing that way with the noise staying in the boat.
The fact that the noise isn't present with the ipod only, yet the noise is there with the HU or EQ only, isn't particularly telling.
Rather than check my ground on the in-boat amplifier, I would re-do all connections related to that amplifier ground.
I would also check for the noise on the in-boat amplifier with each of six speakers and wiring in isolation.
If you find a specific speaker relationship is a culprit then run a substitute speaker wire. Keep in mind that the speaker ground and RCA signal grounds are typically common through the signal path but isolated from the power supply ground. Also keep in mind that the polarity of one side of the amplifier is inverted to facilitate bridging. So it's critical that the left/right grounds remain totally insulated and isolated from one another.
After adding external amplifiers I assume that the existing in-boat speaker wires were entirely isolated from the HU harness.
For noise diagnosis start with the last component in the signal path and work in reverse. Then when the noise reappears you can narrow your focus to a very specific product or interface of products.
In the end, you may need a substitute of the identical in-boat amplifier to confirm or eliminate that product.

Jason,
I'm going to make a few assumptions here including:
When you say the boat is not running you also mean that the key was completely 'Off' yet there is still noise.
When you reversed the RCAs at the EQ end, you also reversed the in-boat and tower output sections of the EQ and tried it playing that way with the noise staying in the boat.
The fact that the noise isn't present with the ipod only, yet the noise is there with the HU or EQ only, isn't particularly telling.
Rather than check my ground on the in-boat amplifier, I would re-do all connections related to that amplifier ground.
I would also check for the noise on the in-boat amplifier with each of six speakers and wiring in isolation.
If you find a specific speaker relationship is a culprit then run a substitute speaker wire. Keep in mind that the speaker ground and RCA signal grounds are typically common through the signal path but isolated from the power supply ground. Also keep in mind that the polarity of one side of the amplifier is inverted to facilitate bridging. So it's critical that the left/right grounds remain totally insulated and isolated from one another.
After adding external amplifiers I assume that the existing in-boat speaker wires were entirely isolated from the HU harness.
For noise diagnosis start with the last component in the signal path and work in reverse. Then when the noise reappears you can narrow your focus to a very specific product or interface of products.
In the end, you may need a substitute of the identical in-boat amplifier to confirm or eliminate that product.

David

David, sometimes I read your responses and get confused quickly so I'm going to take these one at a time...

When you say the boat is not running you also mean that the key was completely 'Off' yet there is still noise.This is a 2003 SANTE, so I have the pushbutton keypad. The code is punched in and push Start to "power-up" the boat electronics. I then push the source button on the HU remote to powerup the stereo system. This is a normal resting mode for the boat and I guess the same as powering up the stereo with an accessory switch. No ignition start signal or engine running until I push the start button a second time.

When you reversed the RCAs at the EQ end, you also reversed the in-boat and tower output sections of the EQ and tried it playing that way with the noise staying in the boat.I'm assuming you are asking this for clarrification? I swapped the in-boat and tower RCAs at the EQ and the noise stayed at the in-boats. I also tried this at the amp end of the RCAs as well with the same result.

Rather than check my ground on the in-boat amplifier, I would re-do all connections related to that amplifier ground.I have 1/0 gauge power and ground cables running directly from the house batteries to distribution blocks. From there separate 4 gauge cables go to each of my 3 amps and a small power distribution panel for powering the HU, EQ, and remote turn-on relay. So are you telling me to re-do all the ground connections on my 1/0 gauge cable or 4 gauge cables?

I would also check for the noise on the in-boat amplifier with each of six speakers and wiring in isolation. This is one thing I have not done is separate the speaker side to look for problems. I will try that this weekend.

After adding external amplifiers I assume that the existing in-boat speaker wires were entirely isolated from the HU harness.Yes. I removed all the original speaker wiring and replaced it with new larger gauge wiring. None of the speaker wiring terminates at the HU, only amps.

For noise diagnosis start with the last component in the signal path and work in reverse. Then when the noise reappears you can narrow your focus to a very specific product or interface of products. This is why I started with plugging the iPod directly to the amp. I figured if the noise went away (which it does) then my problem was ahead of the amp. I guess since the iPod only sends a small pre-amp voltage the noise may just be inaudible. The noise did drop a noticable amount when I moved the RACs from the EQ to the HU which also drops the pre-amp voltage about 4V. Dropping it to whatever mV may just be enough to where I can't hear it.

In the end, you may need a substitute of the identical in-boat amplifier to confirm or eliminate that product. I hope not! Wifey will not be happy if I have to buy an amp just to test a problem. If it comes to that I will probably just deal with it. The noise is inaudible once I play music. It's just annoying during mid-song or not playing intervals, plus I spent too much time and money for it to make noise I don't want.

Jason,
Substitute product: An authorized dealer can send you a replacement for testing purposes. The transaction can be canceled long before your statement arrives. Standard practice.
For system set-up you follow the signal path. For noise you reverse the signal path and begin with the last component. Bouncing around muddies the clarity of your diagnosis and confuses you.
Only you know if your grounds are rock solid. A measurement based on a multimeter isn't very telling in some diagnostic applications because there is virtually zero current being passed. More current exposes issues for the first time. Give 'em all a serious tug.
Sometimes a boat ignition or engine management module is activated the moment the key is 'On', whether it is in the 'Ign' or 'Acc' position. And this module can induce some wicked noise. It's easy to temporarily wire the source 'Hot' all the time for a short term test.
You said you measured the RCA resistance. More important would be to measure the in-boat amplifier internal resistance between a) the RCA input shield and the speaker output ground (remember the reversed polarity on one channel), and b) the resistance between the RCA input shield and power supply/primary ground. Every input should have a very consistent reading with everything unplugged. Do the same test on the EQ.
It's a lot easier to do an diagnosis exchange by phone. Diagnosis by email or PM or a public forum is too tedious. No doubt.
Still the biggest issue that troubles me is that you can eliminate the noise from ALL channels by unplugging just ONE channel. That brings me to the conclusion that you may have a legit problem....and you should resolve it during the warranty period IMO.

Removed 2 bow speakers from amp = noise in rear speakers
Removed 4 rear speakers from amp = noise in bow speakers
I read the ohm value for each speaker and found the right rear to have a 2ohm load where the others had a 4 ohm load. Since it is paralleled with the right front speaker my load at the amp was around 1.5ohms. I have removed that speaker from the amp for now, but still have noise. I'm wondering if this one speaker has damaged the amp running that channel below it's rated stereo impedance and that is what has casued my noise to show up. I will contact the manufacturer today and see what insight they might have.

Unfortunately my in-boat amp is out of the warranty period so a rebuild or replace situation may be in order.

Jason,
You are actually reading the DC resistance and not the impedance. It is perfectly normal for the DCR to measure a little lower than the stated nominal impedance. Two 4-ohm speakers in parallel is 2-ohms plus the very small series resistance of the wire. Still, even in consideration of this being a DCR measurement, the 1.5-ohm sounds a bit low.

I would send the amplifier to the manufacturer for testing. I would not buy a replacement until I was confident that I isolated the true cause.